Agilent U12xxx series

The Agilent U12xxx series are handheld digital multimeters, ranging from inexpensive all-purpose meters to industrial meters.

Model	Counts	Supported
U1231A	6000	Yes
U1232A	6000	Yes
U1233A	6000	Yes
U1241A / U1241B	10000	Yes
U1242A / U1242B	10000	Yes
U1251A / U1251B	50000	Yes
U1252A / U1252B	50000	Yes
U1253A / U1253B	50000	Yes
U1271A	30000	No
U1272A	30000	No
U1273A	30000	No
U1273AX	30000	No

Is your model not supported yet? Get in touch! We need people to help us test other models in this series, and getting a new model supported is generally quick & easy.

Connection

All models communicate via an optically isolated serial connection, at 9600 bps, 8 bits, no parity, and 1 stop bit (9600/8n1). Connecting to the devices can be done either via USB (U1173A cable) or Bluetooth (U1177A interface).

Protocol

All models in this series use generally the same protocol, with only minor differences between models – and none within the same range.

The meters will respond to commands, which consist of a short ASCII string followed by either LF or CR+LF. The meter will either send no response at all, some ASCII text followed by CR+LF, or *E followed by CR+LF if the command given was invalid.

Some events (such as turning the rotary switch) will cause spontaneous transmissions of event notifiers. These consist of a * character, a single character and CR+LF.

*IDN?

Sending the command *IDN? causes the device to return a comma-separated four-field string, compatible with the identical GPIB command. The four fields are vendor name, model name, serial number and version:

Agilent Technologies,U1232A,MY52020136,V1.00

*RST

Sending the command *RST causes the device to reset. The response is an asterisk followed by the current dial position, for example *1 indicates the first position.

SYST:BATT?

The command SYST:BATT? returns a value indicating the device's battery level. The value is in a different format depending on the model series:

The U123xx models return a percentage value, like this:

36%

The U124xx models return a value like this:

+1.04200000E+02

SYST:BEEP

The command SYST:BEEP TONE make the multimeter emit a beep.

SYST:BLIT

The commands SYST:BLIT 1 and SYST:BLIT 0 turn the screen backlight on and off. There is no response. The backlight timer will still run and turn the backlight back off again if it is enabled.

FETC?

The FETC? command returns the current measured value, as a floating point ASCII string, as in the following examples:

+9.25000000E-03
+0.00000000E+00
-1.01140000E+00
-9.10200000E-01

The sign characters are always present, and the value is always in normalized scientific format. This applies even when in a mode that uses integer numbers, 11 would be transmitted as +1.10000000E+01. If no valid measurement is available, i.e. the display shows "OL" or "-OL", the transmitted value is either +9.90000000E+37 and -9.90000000E+37 respectively.

CONF:

The CONF: commands can be used to change modes and ranges on the multimeter. It is not to be confused with the CONF? query described below.

For a given rotary switch position, only those CONF: commands work that switch to modes that can be reached by pressing the range or shift buttons.

U123xx models

Command	Rotary Switch Setting	Meaning
CONF:VOLT:AC	Any voltage mode	Switch to Volts AC mode with autoranging
CONF:VOLT:DC	Any voltage mode	Switch to Volts DC mode with autoranging
CONF:VOLT:AC 600	Any voltage mode	Switch to Volts AC mode and 600V range. Valid ranges are: 600, 60, 6, 0.6
CONF:VOLT:AC 600	Any voltage mode	Switch to Volts AC mode and 600V range. Valid ranges are: 600, 60, 6, 0.6
CONF:CURR:AC	Any current mode	Switch to AC current measurement mode with autoranging
CONF:CURR:DC	Any current mode	Switch to DC current measurement mode with autoranging
CONF:CURR:AC 60u	Any current mode	Switch to AC current measurement mode and 60uA range. Valid ranges are 10, 6 for A mode, and 600u, 60u for uA mode.
CONF:CURR:DC 60u	Any current mode	Switch to DC current measurement mode and 60uA range. Valid ranges are 10, 6 for A mode, and 600u, 60u for uA mode.
CONF:FREQ	VZlow, AC voltage or any current mode	Switch to frequency measurement mode. No manual ranges are available.
CONF:CONT	Resistance	Switch to continuity mode.
CONF:RES	Resistance	Switch to resistance mode with autoranging.
CONF:RES 6M	Resistance	Switch to resistance mode and 6MΩ range. Valid ranges are 60M, 6M, 600k, 60k 6k, 600
CONF:CAP	Capacitance	Switch to capacitance mode with autoranging.
CONF:CAP 1000n	Capacitance	Switch to capacitance mode and 1000nF range. Valid ranges are: 10m, 1000u, 100u, 10u, 1000n

U124xx/U125xx models

Same as above for the U123xx, except for different ranges.

CONF?

The CONF? command queries the device's current measurement configuration.

U123xx models

This can be either one, two or three comma-separated fields. The number of fields depends on the first field's value, but the second field always denotes the measurement mode's range and resolution, and the third field is the current type (AC or DC). For example, this indicates AC voltage in the 600mV range:

V,0,AC

Mode	Resolution	Current	Meaning
V	y	y	Volts
	0		Range 600mV, resolution 0.1mV
	1		Range 6V, resolution 1mV
	2		Range 60V, resolution 0.01V
	3		Range 600V, resolution 0.1V
MV	y	y	Millivolts
	1		Range 600mV, resolution 0.1mV
A	y	y	Ampere
	0		Range 6A, resolution 1mA
	1		Range 10A, resolution 0.01A
UA	y	y	Microampere
	0		Range 60μA, resolution 0.01μA
	1		Range 600μA, resolution 0.1μA
FREQ	y	y	AC frequency
	0		Always shows 0, even when the range is changed manually on the device. This is possibly a firmware bug.
RES	y	n	Resistance
	0		Range 600Ω, resolution 0.1Ω
	1		Range 6kΩ, resolution 0.001kΩ
	2		Range 60kΩ, resolution 0.01kΩ
	3		Range 600kΩ, resolution 0.1kΩ
	4		Range 6MΩ, resolution 0.001MΩ
	5		Range 60MΩ, resolution 0.01MΩ
CAP	y	n	Capacitance
	0		Range 1000nF, resolution 1nF
	1		Range 10μF, resolution 0.01μF
	2		Range 100μF, resolution 0.1μF
	3		Range 1000μF, resolution 1μF
	4		Range 10mF, resolution 0.01mF
DIOD	n	n	Diode

U124xx and U125xx models

The output consists of a quoted string with the meter's mode, followed by a space, two values, separated by a comma, denoting the current range, and the value of one count. The mode may optionally include a colon followed by a code denoting a submode relevant to that major mode. For example, AC voltage mode with 1000mV range on a 10000-count U1241B would be given as:

"VOLT:AC +1.000000E+00,+1.000000E-04"

Mode	Meaning
VOLT	DC voltage
VOLT:AC	AC voltage
CURR	DC current
CURR:AC	AC current
FREQ	Frequency counter
DIOD	Diode check. No range values are given.
CONT	Continuity. No range values are given.
RES	Resistance
CAP	Capacitance
SCOU	Switch counter. No range values are given.
CPER:0-20mA	Current loop, 0-20mA setting
CPER:4-20mA	Current loop, 4-20mA setting
T1:K or T2:K	Temperature on T1 or T2, submode can be K or J, denoting the thermocouple type. Instead of range values, CEL or FAR is given, denoting the measurement is in degrees Celsius or Fahrenheit. The full response might thus be: "T1:K CEL".

STAT

The STAT? command is used to query the current state of the device. The response is a quoted 21-byte string, like this:

"000000000110L00000000"

U123xx models

Byte	Value	Meaning
1		Max/min/avg mode
	0	Off
	1	On
2		Relative measurement. The last value returned from FETC? before this mode was enabled denotes the stored reference value.
	0	Off
	1	On
3		Trig hold-log
	0	Off
	1	On
4		Auto hold-log
	0	Off
	1	On
5		LED flashlight
	0	Off
	1	On
6		LCD backlight
	0	Off
	1	On
7		Smoothing
	0	Off
	1	On
8		Temp/aux mode. When on and rotary switch is in position 5 (capacitance), CONF? returns MV,1,DC, but the value returned from FETC? instead denotes the temperature, in the unit (F or C) according to the meter's configuration.
	0	Off
	1	On
9		Unknown (always 0)
10		Beep frequency
	0	4.2kHz
	1	3.8kHz (default)
	2	3.4kHz
	3	3.2kHz
	4	Off
11		Auto power-off (APO)
	0	Off
	1	On
12		Unknown (always 0)
13		Unknown (always L)
14-15		Unknown (always 0)
16		Rotary switch position
	0	V/Zlow
	1	Voltage AC
	2	Voltage DC
	3	Resistance
	4	Diode
	5	Capacitance
	6	Current
	7	Microcurrent
17		Continuity mode. When enabled, the value returned from FETC? is either NAN (no continuity) or any real value to denote continuity.
	0	Off
	1	On
18		Unknown (always 0)
19		Battery low indicator
	0	Battery OK
	1	Battery low
20-21		Unknown (always 0)

U124xx models

Byte	Value	Meaning
1		Max/min/avg mode
	0	Off
	1	On
2		Relative measurement. The last value returned from FETC? before this mode was enabled denotes the stored reference value.
	0	Off
	1	On
3		Unknown
4		Unknown
5		Unknown
6		Current loop mode
	0	0-20mA mode
	1	4-20mA mode
7		Unknown (always I)
8		Hold mode.
	0	Off
	1	On
9		Unknown
10		Beep frequency
	0	Off (no beeps)
	C	300Hz
	F	600Hz
	1	1200Hz
	2	2400Hz
11		Auto power-off (APO)
	0	Off
	1	On
12		LCD backlight
	0	Off
	1	On
13		Unknown (always L)
14		Unknown
15		Unknown
16		Rotary switch position
	0	Voltage
	1	Diode
	2	Resistance
	3	Capacitance
	4	uA
	5	mA
	6	A
	7	Temperature
17		Unknown
18		Unknown (always 1)
19		Unknown
20		Switch counter mode
	0	increase count on rising flank (initially low)
	1	increase count on falling flank (initially high)
21		Auto range
	0	Off
	1	On

U125xx models

Byte	Value	Meaning
1		Max/min/avg mode
	0	Off
	1	On
2		Relative measurement. The last value returned from FETC? before this mode was enabled denotes the stored reference value.
	0	Off
	1	On
3		dB mode
	0	Off
	m	?
	V	?
4		Unknown
5		Peak hold mode
	0	Off
	1	On
6		Current percent
	0	0-20mA
	1	4-20mA
7		Triggerhold I/B ?
8		Triggered hold mode.
	0	Off
	1	On
9		Zero temperature compensation?
10		Beep selection ?
11		Auto power-off (APO)
	0	Off
	1	On
12		LCD backlight
	0	Off
	1	On
13		Unknown (always L)
14		Unknown (always 0)
15		Unknown
16		Rotary position ?
17		Output status active/standby ?
18		Unknown
19		Battery low indicator
	0	Battery OK
	1	Battery low
20		Frequency counter prescaler
	0	No prescaling
	1	Divide by 100
21		Auto range
	0	Manual range
	1	Auto range

Event Notifiers

String	Meaning
*0 through *7	Rotary switch position has changed. *0 denotes the most counter-clockwise position (excluding the OFF position), then the value is increased by one for each step in the rotary switch's range.
*B	Battery voltage dropped to "battery empty" level.
*E	Invalid command.
*I	Probes are connected to the wrong sockets for this mode, "Cerr" is shown on display (not supported on U123xx.)
*L	A button was pressed (not supported on U123xx.) This notifier is only sent once after a command, even if the user presses several buttons.

Hold-Log Mode Notifiers (U123xx only)

In Trig Hold-Log mode or Auto Hold-Log mode, the U123xx series multimeters will transmit a quoted 15 byte string, followed by CR+LF, like this example whenever a new value has been captured:

"050000210000200"

Note that the position of the decimal point is not explicitly given, it must be discerned from the range.

Byte	Value	Meaning
1		Unknown (always 0)
2		Function
	0	AUX
	1	Voltage
	2	Microcurrent
	4	Current
	5	Resistance or continuity
	6	Diode
	8	Capacitance
	9	Frequency
3		Unknown (always 0)
4		First (most significant) digit of measurement
5		Second digit of measurement
6		Third digit of measurement
7		Fourth (least significant) digit of measurement
8		Mode bits (several can be set at once)
	1	Autoranging is enabled
	2	Value is negative
9		Mode bits (several can be set at once)
	1	DC
	2	AC
	4	Overload
10		Range, values are the same as with CONF?
11		Unknown (always 0)
12		Temperature unit (probably)
	0	not in temperature mode
	1	degrees Fahrenheit (not confirmed, need to check)
	2	degrees Celsius
13		Mode bits (several can be set at once)
	1	Relative mode is enabled
	2	Trig Hold-Log mode is enabled
	4	Auto Hold-Log mode is enabled
14		Capacitance/AUX mode
	0	Capacitance
	1	AUX temperature (mV setting in menu is off)
	2	AUX mV (mV setting in menu is on)
15		Unknown (always 0)

Resources

• Series overview
• Documentation